Modern ships and boats rely upon high-powered propulsion systems in order to successfully navigate through their respective environments. The delivered power of engines for typical commercial marine vessels ranges between 230-2700 hp (169-2013 kW)1. In order for these vessels to function properly, heat must be dissipated effectively in order to achieve the optimal efficiency for sailing conditions.
There are two main types of cooling systems for marine engines; the first is known as a raw water system and the second is known as the freshwater (closed) cooling system. In a raw water system, surrounding water is drawn from the outside of the ship and is circulated through the engine block and then expelled from the exhaust. This is hazardous to the system in both salt- and fresh-water application due to the corrosiveness of salt on the water pump impellers and the risk of foreign contaminants which could lead the system to foul. The engine components risk early failure and may lead to an engine overhaul before the vessel operator’s expected to.
The second type of cooling system is known as a closed cooling system. These systems do not employ water as a direct cycling fluid rather, rather piping is used to separate the coolant and the surrounding medium. Some systems function similar to the radiator in automobiles where coolant is pumped through one side of a heat exchanger and raw water is pumped through another in order to dissipate heat. Another type of closed cooling system removes the need for a heat exchanger by employing an external set of pipes which protrude from the bottom of the vessel to exchange heat directly with the surrounding water. Keel coolers operate by taking advantage of the surrounding water as an endless heat sink for a vessel’s heat transfer fluid. Due to the risk of fouling from various contaminants contained in the water medium, these coolers typically do not run ocean water directly through the power cycle, but rather exchange heat via convection through external tubing between the engine coolant and the surrounding medium. This process is illustrated in Figure 1, explaining just how this process takes place. A pump draws coolant from the thermostat and sends it through and expansion valve, which sends coolant into the keel cooler at the bottom of the vessel. The heated fluid moves through a series of highly conductive pipes which remove the heat via convection with the heat sink. The cod coolant is finally pumped back into the engine via a cooling pump. This process eliminates the need for a heat exchanger, and other components vital for closed cooling systems.
Cummins Marine is one of the different specialized markets of Cummins Inc. which specializes in the “Marinization” of engines and the design of new components to allow the current Cummins engine line survive in marine applications. Customers often times ask the Application Engineers to ensure the engine selected will work properly with the vessel it is going to be installed in. This includes the sanity check of ensuring that the keel cooler will provide the correct cooling for the engine. These factors are important to consider since the vessel must pass an Installation Quality Assurance Review in order to meet warranty. In order to meet customer’s requirements, Cummins Marine makes use of a web-based optimization tool which allows the Application Engineers to predict whether or not a particular keel cooler design will successfully meet the vessels’ requirements. The program operates on user-inputted parameters such as keel size, engine power, and temperature range. These values then predict whether the cooler will pass or fail based on extreme operating conditions. Although the tool has been in service for a long time, it has several limitations. The tool only predicts keel cooler systems which are made from steel and does not offer an option to optimize the design. The program lacks feedback and is outdated as a user interface. The goal of the Keel Cooler Optimization Tool Senior Design Project is to create a tool that adds feedback alongside the pass-fail conditions. The program will suggest improvements in the design of the keel cooler based on a thermodynamic analysis. Such improvements can range from material selection, pipe configuration as well as an optimal temperature range of operating conditions. The successful implementation of this tool will result in an increase in company profit and customer satisfaction. With a program which successfully predicts improvements in keel cooler design, boat builders will be able to build the keel coolers with confidence knowing it will be more efficient and optimize the performance of their engine and work in different nautical waters.
To achieve this goal, extensive background research must be conducted on the variables important to the design of a keel cooler. Once the group has a full understanding of the analysis process, the method for creating this tool must be decided upon; this includes the programming language, program structure, user interface and a means for testing the accuracy of the program. The group must show sufficient understanding of the thermal design process and develop a product that is user-friendly, intuitive and provides meaningful feedback to the end user.
The group designed a working prototype that validated the engineering calculations by simulating various configurations of a keel cooler.
